In LED lighting, an electronic driver or a LED driver in short converts an AC voltage provided from an AC mains to a DC output current for driving a LED load such as a retrofit LED tube. The conversion is done by first rectifying the AC voltage to a DC voltage and then using a DC-to-DC switching-mode power converter to generate the DC output current. In the electronic driver, an isolation transformer is sometimes not installed between the AC mains and output ports of the power converter for cost saving. In the absence of the isolation transformer, there is a risk that a person receives an electric shock.
In particular, the risk is suspected to be increased after the introduction of retrofit LED tubes for replacing conventional fluorescent tubes. For illustrating this risk, FIG. 1 depicts a typical situation that a person 80 inserts a retrofit LED tube 10 to a lamp holder 20 for receiving electrical power from an AC mains 30. Typically, the LED tube 10 integrates a LED load and an electronic driver so that an external driver (or a ballast) is not required. As a result, the AC mains 30 may be connected directly to two ends of the lamp holder 20. When the person 80 inserts the LED tube 10 into the lamp holder 20, one end 11 of the LED tube 10 is inserted into the lamp holder 20 while it is possible that the person 80 holds another end 12 of the LED tube 10. Different from a fluorescent tube, whose two ends are separated by a gas that typically forms an insulator unless ionization occurs, the LED tube 10 contains electronics and there may be a circuit path between the two ends 11, 12, posing a risk of electric shock to the person 80.
In the art, most of the effort on electric-leakage protection for the electronic driver has been focused on overcurrent protection, e.g., US2012/0086356 and US2016/0120002, rather than prevention of electric shock to the personnel. There is a need in the art to have an electronic driver that drives a LED load and at the same time provides electric-shock protection to a person when the person inserts a LED lamp integrated with the electronic driver and the LED load to an AC mains.